This application is the national phase of PCT application PCT/JP01/00589, filed Jan. 29, 2001, which designated the United States but was not published in English, the disclosure of which is incorporated herein by reference.
The present invention relates to a thermal spraying torch, which is used in the case of carrying out a surface treatment using a thermal spray material heated and fused by a plasma forming gas or combustion gas. In particular, the present invention relates to a thermal spraying torch, which is suitable for carrying out a surface treatment with respect to an inner surface of pipes, cylinders and the like.
Pipes such as those for cooling medium used in boilers and power generators, pipes connecting chemical reaction equipment, pipes for delivering chemicals and carrying special materials are used under severe conditions; as a result, these pipes are easy to corrode. For this reason, the inner surface of pipes must receive a suitable surface treatment so that corrosion resistance can be improved.
Likewise, there is a great need for carrying out the surface treatment with respect to each inner surface of many cylinders 91 formed in a cylinder block 90 as shown in FIG. 12. The cylinder block 90 shown in FIG. 12 is used for an engine of automobile, for example. In this case, there is a need to reduce the entire weight of the automobile; for this reason, the cylinder block 90 is formed of a light aluminum alloy. An iron coating film must be formed on the inner surface of each cylinder 91 so that the inner surface of the cylinder can withstand repeated sliding contact of the pistons.
Plating may be used as the surface treatment with respect to the inner surface of the pipes and the cylinder 91. However, in this case, depending on the plating technique, merely a thin coating of film is formed, and further, in the case of plating a large-sized work piece, such as the cylinder block 90, considerably large plating equipment is required. In view of the above circumstances, so-called xe2x80x9cthermal spraying technologyxe2x80x9d has attracted special interest recently as a technology capable of creating the required coating thickness comparatively easily.
However, the conventional thermal spraying technology is employed in cases where a thermal spray work piece is a flat shape as disclosed in JP 61-149264 A (Unexamined Patent Publication (Kokai) No. TOKKAISHO 61-149264) and JP 61-149265 A (Unexamined Patent Publication (Kokai) No. 61-149265), or in cases where the work piece is a large curved shape as disclosed in JP 56-100666 (Unexamined Patent Publication (Kokai) No. 56-100666). Thus, there has been almost no thermal spraying technology for carrying out a surface treatment with respect to a cylindrical inner surface such as the inner surface of pipes or the inner surface of a cylinder 91.
In view of the above circumstances, the present inventor has already proposed a thermal spraying torch, which is suitable for carrying out thermal spraying with respect to the inner surface of the pipe and the cylinder 91 in JP 5-29092 B (Examined Patent Publication (Kokoku) No. 5-29092). The thermal spraying torch disclosed in the above Publication is provided with a rotatable discharge member attached to the distal end portion, and further, the discharge member is formed with a pressure-receiving portion at the outer periphery. A gas is sprayed onto the pressure-receiving portion, and thereby, the entirety of the discharge member can be rotated. Of course, a droplet 81 is jetted from the discharge member. When being jetted, the droplet 81 is radially discharged, and thereby, thermal spraying is carried out with respect to the inner surface of the pipe and the cylinder 91 by the rotation of the discharge member and the radially discharged droplet 81.
Thereafter, the present inventor has studied the thermal spraying torch proposed in the above JP 5-29092 B (Examined Patent Publication (Kokoku) No. 5-29092). As a result, the present inventor has discovered that in the known thermal spraying torch a uniform coating 82 is difficult to form. The present inventor discovered that the discharge member does not reach a sufficiently high rotational speed (3,000 rpm or more), which he found was required for forming a uniform sprayed coating film 82 on the cylinder inner surface of a cylinder 91. The present inventor then investigated the reasons why the required rotational speed was not obtained. Although not wishing to be bound, the present inventor considers that in the thermal spraying torch proposed in JP 5-29092 B (Examined Patent Publication (Kokoku) No. 5-29092), in order to spray a gas onto the pressure receiving portion formed at the outer periphery of the discharge member, the main body positioned outside the discharge member must be formed with a first passage for supply of the gas. However, due to the design, the inner diameter of the first passage cannot be set too large, and thereby, the amount of gas supplied to the outer periphery of the discharge member is limited. As a result, the discharge member cannot attain a satisfactory, desired high rotational speed, which denies the regular forming of a uniform sprayed coating film 82.
Of course, in cases where a material such as zinc having a relatively low melting point is used as a thermal spray material, the high rotational speed as described above is not required. Further, in order to prevent mechanical damage to this type of rotary torch, there are some cases where it is desired that the rotational speed is as low as possible.
Further, the present inventor has conducted various studies as to determine the setting of the rotational speed of the discharge member in the ranges of 800 to 6,000 rpm and as a result, the present invention has been made.
In the Summary and in the xe2x80x9cBest Mode for Carrying out the Inventionxe2x80x9d like reference numerals are used in describing constituent components or process steps included in first and second aspects of the present invention.
An object of the present invention is to provide a thermal spraying torch 100, which can set a rotational speed of discharge member for radially discharging droplets 81 to a range from 800 to 6,000 rpm, and can carry out thermal spraying with respect to the inner surface of a pipe or a cylinder 91.
Another object of the present invention is to provide a thermal spraying torch 100, which can set a rotational speed of discharge member for radially discharging a droplet(s) 81 to a suitable value, e.g., 3,000 rpm within a range from 800 to 6,000 rpm, and can carry out thermal spraying with respect to the inner surface of a pipe or a cylinder 91, and further, can protect bearings supporting the discharge member so that high durability can be obtained.
In order to achieve the above objects, according to a first aspect of the invention, the present invention provides a thermal spraying torch 100 that is capable of successively supplying a thermal spray material 80, which can be heated and fused by a plasma forming gas formed by an arc generated between electrodes contained in an outer cylinder 10 or by a combustion gas supplied passing through an outer cylinder 10 and burned under high temperature state, and spraying the thermal spray material 80 via a nozzle 40 using the plasma forming gas or the combustion gas so that a droplet(s) 81 can be formed. The thermal spraying torch 100 further includes a rotating discharge member 60, which is contained at a forward portion of the nozzle 40 and has a droplet passage 61 for the droplet(s) 81 at the center so that the droplet(s) 81 can be jetted together with the plasma forming gas or the combustion gas. The discharge member 60 is formed with a projection 63, which changes a discharge direction of a droplet(s) 81 at the center of the distal end portion, and is formed integrally with a plurality of arm members 65, which are projected from the discharge member 60 and arranged in an air jet cylinder 50 contained in the outer cylinder 10 at the rear end, whereby an air jet space 66 for jetting a rotation air is formed, and a rotational force can be given to the discharge member 60 by jetting air from an air jet port 53 of the air jet cylinder 50 arranged outside the air jet space 66.
That is, the thermal spraying torch 100 described in the first aspect of the invention, can include the same discharge member 60 as that of the thermal spraying torch proposed already by the present inventor in the above JP 5-29092 B (Examined Patent Publication (Kokoku) No. 5-29092). The discharge member 60 is formed integrally with a plurality of arm members 65, which are projected from the discharge member 60 and arranged in an air jet cylinder 50 contained in the outer cylinder 10 at the rear end. A plurality of arm members 65 is formed at the rear end of the discharge member 60, and thereby, the air jet space 66 for jetting a rotation air is formed at the rear end of the discharge member 60 and in the air jet cylinder 50 contained in the outer cylinder 10.
Therefore, as shown in FIG. 2 to FIG. 4 and FIG. 8, in the thermal spraying torch 100, the entire periphery of the air jet cylinder 50 covering all arm members 65 of the discharge member 60 is formed with the rotation air passage 13. By doing so, it is possible to jet a gas (usually, compressed air or incombustible gas) in an amount sufficient to rotate the discharge member 60 at high speed from many air jet ports 53 formed in the air jet cylinder 50 toward each arm member 65.
The thermal spraying torch 100 according to an embodiment shown in FIG. 2 to FIG. 4 is a torch of a so-called xe2x80x9cgas wire flame sprayingxe2x80x9d type thermal spraying equipment. As shown in FIG. 4, the thermal spray material 80 is fused by the combustion gas supplied through the outer cylinder 10 and burning under high temperature state. Thereafter, the fused thermal spray material 80 is sprayed by the combustion gas and the above gas such as air after a rotational force is given to the discharge member 60, and thereby, the droplet 81 can be formed.
As shown in FIG. 3, a fuel gas and an auxiliary gas such as oxygen are supplied to a fuel gas passage 11 and an auxiliary gas passage 12 formed in the thermal spraying torch 100 via a fuel gas supply tube 11a and an auxiliary gas supply tube 12a connected individually to a support member 20 constituting the thermal spraying torch 100. Then, the fuel gas and the auxiliary gas are mixed in a mixing chamber 36 formed by a tributary member 30. The fuel gas and the auxiliary gas thus mixed are supplied to a mixed gas hole 43 formed in a nozzle 40 via a mixed gas hole 34 of the tributary member 30, and then, are jetted from the distal end of each mixed gas hole 43 into the droplet passage 61 of the discharge member 60. In this case, the mixed gas is ignited by an external igniter, and is used as high temperature combustion gas capable of fusing the thermal spray material 80.
The thermal spray material 80 has a line-like form made of a steel material, for example. In particular, as shown in FIG. 3, the thermal spray material 80 is supplied by an external equipment of the thermal spraying torch 100 via a center hole 22 of the support member 20, a center hole 32 of the tributary member 30 and a center hole 42 of the nozzle 40, which are mutually connected. In this case, the thermal spray material 80 is supplied so as to successively project from the distal end of the nozzle 40, that is, from the flame 15 shown in FIG. 4 at a constant speed.
Additionally, in the thermal spraying torch 100, the discharge member 60 is rotated at a high speed, and at the distal end of the nozzle 40, the thermal spray material 80 is fused by the combustion gas so that droplets 81 can be formed. In this case, as shown in FIG. 4, the air rotating the discharge member 60 passes through an air passage 62 of the discharge member 60 at high speed, and further, the discharge member 60 is formed with a projection 63 for bending the direction of the air passage 62 at angle of about 100 degree at the distal end. Therefore, the droplets 81 can be radially jetted as shown by a dotted line of FIG. 1 and FIG. 4.
In the thermal spraying torch 100, the droplets 81 can be formed from a thermal spray material 80 by a plasma forming gas formed using an electric arc technique. In such a case, the above nozzle 40 or the thermal spray material 80 passing through it is used as a negative electrode, and the discharge member 60 is used as a positive electrode. In this case, in place of the fuel gas, the plasma forming gas may be passed through the fuel gas passage 11 and the auxiliary gas passage 12.
Therefore, the thermal spraying torch 100 is inserted into each cylinder 91 of a cylinder block 90 at a constant speed as shown in FIG. 12, and thereby, a sprayed coating film 82 as shown can be formed on the inner surface of each piper or cylinder 91. Of course, since the discharge member 60 is rotated at a high speed, a sprayed coating film 82 having a uniform thickness (in this embodiment, about 0.1 to 0.3 mm) is formed on the cylindrical inner surface of each pipe or cylinder 91.
Further, in order to achieve the above objects, according to a second aspect of the invention, the present invention provides a thermal spraying torch 100, successively supplying a thermal spray material 80 heated and fused by a plasma forming gas formed using an arc between electrodes contained in an outer cylinder 10, or by a combustion gas supplied passing through the outer cylinder 10 and burned under high temperature state, and spraying the thermal spray material 80 via a nozzle 40 by the forming gas or the combustion gas so that droplets 81 can be formed, and further, including a rotatable discharge member 60, which is contained at a forward portion of the nozzle 40 and has a droplet passage 61 for the droplets 81 at the center so that the droplets (81) can be jetted together with the forming gas or the combustion gas, wherein the discharge member 60 is formed with a projection 63, which changes a discharge direction of a droplet(s) 81 at the center of the distal end portion, and is formed integrally with a plurality of arm members 65, which are projected from the discharge member 60 and arranged in an air jet cylinder 50 contained in the outer cylinder 10 at the rear end, thereby forming an air jet space 66 for jetting a rotation air and a plurality of retractable support spaces 67 opened in a direction perpendicular to the axial line, a rotational force is given to the discharge member 60 by air jetted from an air jet port 53 of the air jet cylinder 50 arranged outside an air jet space 66, and a friction block 70 is movably contained in each retractable support space 67, and an outer surface 71 of each friction block 70 is abutted against the air jet cylinder 50 so that the rotational force is set to a predetermined value or less.
The thermal spraying torch 100 according to a second aspect to the invention may generally have the same basic structure as a thermal spraying torch 100 according to a first aspect of the invention. However, the thermal spraying torch 100 according to a second aspect of the invention differs from the thermal spraying torch 100 according to the first aspect in the following points. More specifically, the discharge member 60 is formed integrally with the plurality of arm members 65 at the rear end. By doing so, as shown in FIG. 7, the air jet space 66 for jetting rotating air and the plurality of retractable support spaces 67 opened in a direction perpendicular to the axial line are formed, and the movable friction block 70 is contained in each retractable support space 67. The thermal spraying torch 100 according to the second aspect is the same as the above-described thermal spraying torch 100 according to the first aspect in that the retractable support spaces 67 are formed, and the friction block 70 is movably contained in each retractable support space 67; therefore, a further detailed explanation may be omitted.
In this embodiment, as shown in FIG. 7, one air jet space 66 for jetting a rotation air and three retractable support spaces 67 opened in a direction perpendicular to the axial line of the discharge member 60 are formed. Further, the air jet space 66 and the retractable support spaces 67 are arranged so as to form the cross-shaped letter. Three removable friction blocks 70 arranged as shown in FIG. 9 are contained in the three retractable support spaces 67, respectively. By doing so, each friction block 70 is abutted against the inner surface of the air jet cylinder 50 positioned directly outside the retractable support spaces 67 by a centrifugal force when the discharge member 60 is rotated at a high speed. In this case, each friction block 70 is contained in each retractable support space 67 so that an outer peripheral surface 71 of the friction block 70 shown in FIG. 9 and FIG. 10 is positioned toward the outside.
As a result, in the thermal spraying torch 100 according to a second aspect, the outer peripheral surface 71 of each friction block 70 is abutted against the inner surface of the air jet cylinder 50 by a centrifugal force when the discharge member 60 is rotated at a high speed. Therefore, a frictional force is generated between the outer peripheral surface 71 of each friction block 70 rotating together with the discharge member 60 and the inner surface of the air jet cylinder 50, which is not rotated because it is provided on the outer cylinder 10. By the frictional force, the rotational force of the discharge member 60 is set at a predetermined value or less.
The frictional force by the friction blocks 70 may be adjusted by making various changes to the number of the retractable support spaces 67, the number of friction blocks 70 contained in these retractable support spaces 67 (e.g., contained in only two of three retractable support spaces 67), and a mass (weight) of the friction block 70. Basically, the total mass of each friction block 70 is changed, or a coefficient of friction between these friction blocks 70 and the air jet cylinder 50 contacting with the blocks are changed.
Therefore, in the thermal spraying torch 100 according to a second aspect of the invention, the brake is applied by a centrifugal force when the discharge member 60 is rotated at a high speed, that is, by the friction blocks 70 contained in the retractable support spaces 67. By doing so, the discharge member 60 enables rotation at a speed no higher than necessary; therefore, damage to each rotatable bearing 64 supporting the discharge member 60 to the outer cylinder 10 and a distal opening 14 of the outer cylinder 10 is avoided. As a result, it is possible to provide a thermal spraying torch having high durability.
A thermal spraying process using a present thermal spraying torch is also provided.